Wide-angle objective lens



MW x mg- Aug. 2, 1960 A. c. s. VAN HEEL ETAL WIDE-ANGLE OBJECTIVE LENS Filed July 24, 1958 SILAKUH KUUM INVDTIORS Abraham Q3 Van Hell Gerardo: J. Baernink Hendrik J. Raterlnk JITTORNEJS United States Patent The invention relates to a wide-angle objective lens.

Wide-angle lens systems for photographic purposes covering a field of view of more than 180' are known in the art. These wide-angle systems comprise two parts, a negative front system operating as a field compressor and comprising one or more negative meniscus lenses having a back surface which is substantially semi-spherical in shape, a fixed diaphragm or stop and behind this a positive part of the system consisting of more than one lens.

The prior art lens with the largest wide-angle covers a field of view of 210, however, owing to the low light intensity in the region of the border of the field it re- 2 quires an exposure time of more than one second under moderately bright weather conditions even if a rapid negative film is applied, its positive part being composed of two lenses: the first, a doublet lens being positioned just behind the stop and the second lens, which has a great focal distance, at a substantial distance behind this.

The object of the invention is to provide for a wide angle objective covering a field of view of up to about 270'.

Another object of the present invention is to provide for a wide-angle objective having sutficient light intensity in the region of the border of the field of view to permit a light exposure time of less than one tenth of a second under moderately bright weather conditions.

2,947,219 Patented Aug. 2, 1960 system comprises at least two negative meniscus lenses having substantially semi-spherical back surfaces, the centre of which being positioned approximately in the plane of the stop, and the positive system comprises (a) a positive lens positioned close behind the stop, giving a positive resulting focal distance, and being a doublet lens composed of a biconcave part and a biconvex part cemented together, (b) a positive lens which may be of the doublet type, (c) a triplet lens composed of a biconcave, a concave-convex and a biconvex part, cemented together and (d) a fourth lens having a great focal length, the total axial thickness of the said positive triplet lens being greater than the focal distance of the complete objective.

The figure of the drawing illustrates an embodiment of the complete objective.

The curvature of the image field of our wide-angle lens is only small and also the other optical aberrations are small as a result of which our lens has proved itself very useful in practice.

A very appropriate embodiment of a lens according to the invention complies with the magnitudes given in Table I and is shown in the drawing.

In the figure X is the stop. A and B are the two negative meniscus component lenses before the stop, while the component lenses C, D, E and F are positioned behind the stop. As shutter mechanism a co rci MM able compur shutter SS! has been mounted in a. suitable.

er e.g. ween the component D e ace r, is preferably present, although this is not strictly necessary. By splitting up lenses by means of cemented surfaces the quality can be even improved further, if desired. It is remarked that the colour aberrations are mainly corrected by the curvature of the surfaces r r,;, r and r,,; the curvature of the image field is highly influenced by surface r the astigmatism by surface r while the correction conditions for the reduction of coma are considerably influenced by surfaces r and r Table I Lens Lens Refractive Abbes Tm! Com- Radius, mm. Axial Diade: Number potanee, mm. nents n -+28. 81 I 1.53996 59.6 13am A d, -1 5o d: 5. n -+18. 54 1. 53996 50.6 BaKZ B d: -0.95

5.22 '1 00 n -l0.00 1. 56732 42. 8 LFG it "0.

0 7 -+10.00 1. 56873 63. 1 PSK2 do -4.40 n 5. B5 d1 -0.25 7| -+43. 53 V 1. 56873 61 1 PSKZ d; -l.00

D f. -+43. 53 VI 1. 58313 59. 3 SE12 dc 3. 00

die-7.00 Tn--12. VII 1. 5927 35.4 F16 ti -1.80

T -+3104 V'HJ'. l. 4875 70. 0 FK5 E dig-4. an

til-+37. 04 IX 1.7130 53. 8 LBKB tin-9.0

' d s-0.2 fit-+147. x 1. 4875 70.0 FKS F tin-4.0

1' (ABC) -34. 8 mm. 1' (ABOD) 8.3mm. lf-19.3mm. (ABODE) -13.3 mm. (ABCDEF) 12. 3 mm. 11'' 9. 5 mm.

In the objective of the invention the field compressor The types of glass BaKZ etc. show the 3 names ofthetypesofglassconcsrned (astheyareproduced bythe GermanflrmofSchottundGen.); f is the focal distance of the lens combination indicated and 1f the axial distance between the focal point and the adjacent lens surface.

The diameter of the diaphragm amounted to 1.4-2.0 mm.

If the diameter of the fixed diaphragm is 2.0 mm., the diameter of the cross-section in the object space of a parallel paraxial pencil of light rays, which after refraction at the front part of the optical system just fills the diaphragm (viz. the diameter of the entrance pupil), is 1.2 mm.; the relative aperture on the optical axis is then, without filter, f/10. The bestrcsults have been obtained with a diaphragm with a diameter of 1.4 mm.

Table H shows the variations in the optical magnitudes of the wide-angle system according to the invention, within which good results will be obtained.

RANGE OF INDIVIDUAL LENS FOCAL LENGTHS IN ORDER ROM FRONT TO REAR With the wide-angle system according to the invention it is only where the field of vision exceeds 2 x 80 (taken from the centre of the view) that a. distortion becomes perceivable. I

Chromaticaberration is mainly only present as chromatic magnifying aberration, which is substantially eliminated with a faintly red filter (e.g. filter No. R586 of Gevaert).

By the use of such a filter satisfactory images are obtained with a usual film, type 120 with a sensitivity of 17/10 Din (=32 ASA) under moderately bright weather conditions, the time of exposure being ,5 second, the

wide-angle objective being mounted i camera of a 75 4 commercially available type (e.g. the Rada Rollfllmhssette type Rietuchelfalz Model 710, produced in Germany).

The diameter of the image on the negative amounts to r component positioned close behind the said stop, and

a backmost biconvex positive'component having a focal length many times greater than the focal length of the total lens system, the improvement comprising, that between the said two positive components there are situated a positive biconvex component and a triplet component consisting of a biconcave, a concave-convex and a biconvex part cemented together, the total axial thickness of the said triplet component being greater than the focal distance of the total objective; the range for the individual focal lengths of the individual components in order from front to rear wherein f represents the focal length of the objective are the Abbe number of the concave-convex part of the said triplet component being about twice as high as that of the biconcave part of said triplet component, both of said parts having a moderately high refraction index, the third (biconvex) part of said triplet component having a high refraction index as compared with that of the other parts and an Abbe number lying between those of the first two parts of the said component, the axial distance between said positive biconvex component and said triplet component being between 0.35 and 0.75 times the focal length of the total objective.

2. A wide-angle objective according to claim 1 characterized by the following magnitudes:

Retrac- Abbe's Lens Axial Lens ttve Number Com- Radius, mm. Distance,

Index ponents mm.

r1 -+28. 81 I 1.53996 59. 6 A d, -1 50 t1 I5. 50 n -+1B. 54 II 1.53906 50.6 B il -0.05 n +5. 15 5. 22 Stop (X)-..- 4 1. 00 n --10.00 III 1.56732 42.8 d 060 O n -+10.00 IV 1. 56873 63. 1 d. 1 4. 40

63 d1 035 f --m V 1. 56873 63. 1 d. -1.00

D 1 III-F43. 63 VI 1. 68313 69. 3 do -3.00

rip-32. 94

tin-7.00 m-12 VII 1.6921 36. 4 tin-1.80

E rig-+3104 V'III 1. 4876 70.0 dis-LN r p-H1204 IX 1.7130 83.8 d -0.0

he -I'l-M dis-0. I r g-+147. x 1. 4875 70.0 F d s-4.0

m--moo f ABOFMSmm. 1' ABC )-8.3 mm. lf-IOJ mm.- 1" ABODEk-Bjmm. j' ODE l-mmm. II -9.8 mm.

2,947,219 V 6 3. A wide-angle objective according to claim 1 characin which r is the radius of curvature, d the axial distance, terized by the following magnitudes: n the refractive index (D-line), f the focal length of the objective and V is the Abbes number of the lens parts Radil of Surfaces 1mm Thlcknesses and mdlcated' Separations 5 References Cited in the file of th1s patent 2 8.2%;2ig-1 UNITED STATES PATENTS f 23 2,146,662 Van Albada Feb. 7, 1939 2 187 780 Gehrke et a]. Ian. 23 1940 0.5 1.2 0 03 d 0 o5 +$i 1.5? 0252 113 2050; 2,324,081 Herzberger July 13, 1943 31:14:}? 232; 385215: 23221 251381 D l Ri cio Apr. 11. 1 121211.283; 3351211 22121 1 112: 2 1:; Wai n FREIGN PATENTS 225 398 Great Britain Dec. 4 1924 1.5 .5 2013 31210? 33ii5it23i3 755,955 Great Bntam Aug. 29, 1956 g-gtgg gggt 384,879 Germany Nov. 9, 1923 620,538 Germany on. 23, 1935 672,393 Germany Mar. 1, 1939 diameter of diaphragm 677,592 Germany June 29, 1939 Refractive Indices Dispersion or Abbe Numbers 1.38 m- (1.61 65 V1-l 138 m-4 1.61 55 VH 152 1|H (1.61 VH 162 m-1 1.e1 v.-1 10 152 11H 1.61 50 VH 

